A new MEMS‐based system for ultra‐high‐resolution imaging at elevated temperatures

Abstract

In recent years, an increasing number of laboratories have been applying in situ heating (and ultimately, gas reaction) techniques in electron microscopy studies of catalysts and other nanophase materials. With the advent of aberration-corrected electron microscopes that provide sub-Angström image resolution, it is of great interest to study the behavior of materials at elevated temperatures while maintaining the resolution capabilities of the microscope. In collaboration with Protochips Inc., our laboratory is developing an advanced capability for in situ heating experiments that overcomes a number of performance problems with standard heating stage technologies. The new heater device allows, for example, temperature cycling from room temperature to greater than 1000 degrees C in 1 ms (a heating rate of 1 million Centigrade degrees per second) and cooling at nearly the same rate. It also exhibits a return to stable operation (drift controlled by the microscope stage, not the heater) in a few seconds after large temperature excursions. With Protochips technology, we were able to demonstrate single atom imaging and the behavior of nanocrystals at high temperatures, using high-angle annular dark-field imaging in an aberration-corrected (S)TEM. The new capability has direct applicability for remote operation and (ultimately) for gas reaction experiments using a specially designed environmental cell.

Structural and Morphological Changes of Co Nanoparticles and Au-10at.%Pd Thin Film Studied by in Situ Heating in a Transmission Electron Microscope

“…Multiple environmental factors such as temperature, electric/magnetic fields, gas, and light affect the state and behavior of materials (Allard et al, 2009;Park et al, 2009;Takeo et al, 2006). An important factor that is characterized during experiments is the temperature measured inside a transmission electron microscope (TEM) (Allard et al, 2009;Asoro et al, 2013;Barwick et al, 2008;Gontard et al, 2014;Ivanov et al, 1995;Kim et al, 2015;Lee et al, 2003;Park et al, 2009;Saka et al, 2008;Takeo et al, 2006;Zhang & Su, 2009).…”

Advanced Methods of Electron Microscopy in Catalysis Research

“…At 700 C (Figure 4.32c), particle B shows crystal lattice fringes and is apparently two separate grains. Changes in lattice structure visible from one image to the next are largely the result of slight shifts in orientation of the particles because of the thermal effects (Allard et al, 2009). In the presented example, the clear homogenization of the three-layer gold-pallidium particles was an expected result, explained by a diffusion mechanism.…”

Accurately measured precipitate–matrix misfit in an Al–Mg–Si alloy by electron microscopy

“…No corresponding number can be deduced for β'' at present, but if the contraction is substantially different, the effect could be measurable with the current method. With a stable specimen-heating system [21,22], strain mapping at aging temperatures can be performed to investigate the matter.With the aid of high-resolution drift-and distortion-corrected ADF-STEM images, we have accurately measured the misfit between the Al matrix and the coherent β'' precipitate phase in an Al-Mg-Si alloy. The misfit in the different directions is highly dependent on the shape of the precipitate cross-section, suggesting that the β'' phase has a significantly elastic atomic structure.…”

“…No corresponding number can be deduced for β'' at present, but if the contraction is substantially different, the effect could be measurable with the current method. With a stable specimen-heating system [21,22], strain mapping at aging temperatures can be performed to investigate the matter.…”